This invention relates to a control system for a pump, for example, a vehicular pump driven by a DC motor.
A conventional pump control system has comprised a vacuum pump driven by a DC motor to generate and supply a negative pressure to a container, a power and a driving transistor interconnected to drive and stop the DC motor in response to the operation of a first pressure sensor disposed on the container to sense a negative pressure within the container, a second pressure sensor disposed on the container to sense the negative pressure within the container, and an alarm lamp serially connected to the second pressure sensor.
Upon the start of an associated internal combustion engine, the alarm lamp is energized and the power and driving transistors have caused the vacuum pump to be driven through the DC motor so as to thereby gradually increase the negative pressure within the container in a negative direction. Upon the negative pressure reaching a first predetermined magnitude, the second pressure sensor has opened its set of normally closed contacts to deenergize the alarm lamp. Upon the negative pressure further increasing in the negative direction to reach a second predetermined magnitude, the first pressure sensor has opened its set of normally closed contacts to cause the vacuum pump to be stopped through the power and driving transistors and the DC motor. When the negative pressure has been negatively less than the second predetermined magnitude, the first pressure sensor has closed its set of now open contacts to again drive the vacuum pump as described above. Thus, the negative pressure within the container has negatively increased to the second predetermined magnitude resulting in the opening of the contact set of the first pressure sensor. The process as described above has been repeated to maintain the negative pressure within the container substantially at the second predetermined magnitude.
Upon the occurrence of a fault on the DC motor or the vacuum pump, the negative pressure within the container becomes negatively less than the first predetermined magnitude so as to cause the second pressure sensor to close its set of now open contacts. Thus, the alarm lamp has been turned on to indicate that fault.
The conventional pump control system as described above has been advantageous in that the system controls the operation of the DC motor and also the turn-on and -off of the alarm lamp to indicate the controlled status of the DC motor and therefore the vacuum pump but the system has been disadvantageous in that the two pressure sensors are required and therefore, the container is necessarily provided with two positions where the two pressure sensors are disposed respectively resulting in a complicated construction.
Accordingly it is an object of the present invention to provide a new and improved pump control system comprising a single pressure sensor and still retaining the advantages of the prior art practice as described above.